Effect of magnetic field on a tuned liquid damper using a magnetic fluid

Abstract

The frequency response of a liquid (TLD) which uses a magnetic fluid (called a tuned magnetic fluid damper (TMFD)) is investigated. A single-degree-of-freedom mass (TMD) analogy is used to define the effective mass, stiffness and damping and these parameters are then estimated from experimental results. A numerical simulation is used to examine the TMFD and appropriate magnetic field conditions for effective damping are predicted. In particular, the performance of the TMFD was improved by switching the applied magnetic field at a point near the resonant frequency of the undamped structure. A liquid (TLD) is a passive mechanical that uses a sloshing liquid to dampen oscillations. Many researchers in the civil engineering field have examined the performance of TLDs. Sun et al. (1) measured liquid motion in TLDs with different tank shapes and different liquid viscosities and described the complex non-linear characteristics using a single-degree-of-freedom mass (TMD) analogy. Modi and Munshi (2) performed a parametric study focused on enhancing the energy dissipation efficiency of a rectangular liquid through introduction of a two-dimensional obstacle. They observed a significant increase, up to 60%, in energy dissipation when using the obstacle. Yamamoto and Kawahara (3) performed a numerical study using a modified ALE method to clarify the effectiveness of structural control by TLDs. Ab ´ e et al. (4) proposed a new active TLD which uses a magnetic fluid to enhance the performance of the TLD and studied its feasibility experimentally. A magnetic fluid is a stable medium which is essentially a fluid but also has magnetic properties comparable to those of a solid magnet. It can be confined, positioned, shaped and controlled by the application of magnetic fields. In the present paper we describe further experiments for this magnetic fluid (TMFD), expanding on the study by Abet al. We also develop an analytical model for the TMFD using an analogy with a mass (TMD) in which the total mass of the magnetic fluid in the container is separated into an effective mass and a non-effective mass. The TMFD parameters and the magnetic fluid hydrodynamic force are calculated from experimental results and then a numerical simulation is carried out in order to test this model of and examine the effectiveness of the TMFD.